1. Field of the Invention
This invention relates to an overhead door system and, more particularly, to an overhead door and overhead door section system and method, the section including a novel section facing fabricated from a higher tensile steel than previously used in the prior art and incorporating a novel end stile and center stile system and a novel truss and backing sheet combination.
2. The Prior Art
Overhead door systems such as found in residential and commercial entrances such as to garages, and the like, generally involve doors having horizontally arrayed sections joined by hinges into a door unit. The door is mounted in a vertical track which curves upwardly into a horizontal position so that the door may be opened upwardly and supported horizontally in an open position. The sections are joined by the hinges along the longitudinal edges of the sections so that the overall door structure will generally conform to the radius of curvature of the track as it changes from vertical to horizontal. Customarily, each of the sections are fabricated separatly and thereafter hinged together along a longitudinal edge to provide the complete overhead door structure.
Historically, the sections are fabricated from a galvanized and/or prepainted sheet metal stock which has been rolled or otherwise formed into the particular section facing, web and parallel interior flange configurations. Vertical stiles are usually secured to the section facing and interior flanges at spaced locations by spotweld or rivet techniques. Most prior art overhead door systems use hinges that are secured directly to the section stiles so that stresses imposed by the raising and lowering of the door are transmitted from section to section through the hinges to the vertical stiles and, correspondingly, from the stiles through the spotwelds to the section facing and flange. However, it is well known in the art that a spotweld in a prepainted and/or galvanized surface can result in a poor bond between the metal surfaces so joined. Spotwelds are also more susceptible to attack by corrosion, thereby further weakening the bond. Additionally, the section facings of the various overhead door section systems of the prior art are fabricated from mild steel sheet metal having a relatively low (average, 33,000 pound) yield strength. Accordingly, extra weight metal and additional reinforcing struts must be incorporated into the door system to provide desired strength characteristics. These reinforcing struts not only detract from the section appearance but also increase the weight of the overall door system. Added weight requires stronger and, therefore, heavier tracks, springs and the like, with a corresponding increase in cost. Prior art overhead door systems fabricated according the foregoing procedure have failed as a result of (a) spotweld failure, (b) the inherent low strength characteristics of mild steel, and/or (c) inadequate strut support. It is also recognized that the formation of spotwelds on the external surface of the section facing detracts from or otherwise mars the visual appearance of the overhead door system. Additionally, spotwelds on the external surface require the section to be painted after fabrication whereas it is well-known in the art that a more uniform and stable paint surface is achieved when the sheet metal is prepainted prior to fabrication.
It is also well known that steel sections alone provide very poor insulation for heated structures. The practice has, therefore, been to furnish overhead door systems with insulated sections as an option. The sections are usually insulated with a suitable insulative material sandwiched between the section facing and a back facing. The construction features of the prior art sections generally require the use of a segmented and, therefore, visually unattractive and non-supportive back facing fabricated from steel or aluminum sheet metal.
One prior art door section system is disclosed in U.S. Pat. No. 3,740,916 wherein a section flange is secured to a vertical stile by means of a plurality of tabs which are adapted to be bent over into openings formed in the stile.
Another door section system is disclosed in U.S. Pat. No. 3,891,021 wherein adjacent sections are joined at the hinge portion.
In view of the foregoing, it would be an advancement in the art to provide an overhead door and overhead door section system and method whereby a higher tensile steel is utilized in the fabrication of the door sections and wherein novel advances are made for securing the section facing and interior flanges to the vertical stiles and hinges. It would be a further advancement in the art to provide a novel overhead door section system and method utilizing the unique properties of high tensile steel to provide a section that does not require additional struts for reinforcement and support to obtain desired strength characteristics. It would also be an advancement in the art to provide improvements in the section facing, stile, insulation, and back facing of a section thereby reducing the time required for fabrication and assembly. Another advancement would be to incorporate the properties of a higher tensile steel into an overhead door system. Another advancement would be to utilize steel sheet prepainted with a hard, high gloss finish and formed into a novel structure which does not require spotwelds or the like for structural bonding. Such a novel overhead door section system and method is disclosed and claimed herein.